Apoptosis or programmed cell death plays an important role in homeostasis of multicellular organisms. This apoptosis maintains organisms by regulating the cell growth and death, but, if it is inhibited by some factors, there may result in pathological diversity including cancers, autoimmune diseases, neurodegenerative disorders, and others [see Thompson, C. B. Science, 267, 1456-1462 (1995); Hanahan, D. & Weinberg, R. A., Cell, 100, 57-70 (2000)].
In the tumor development stages, such regulatory step of apoptosis allows IAPs (inhibitor of apoptosis proteins) to accumulate within cells via overexpression, to inhibit programmed cell death of mutant cancer cells undergoing an apoptotic stage, which leads to the inhibition of the natural apoptotic mechanism in the processes of development, growth, and metastasis of cancer cells by various apoptosis signals (e.g., stimuli such as DNA damage, chemical agents, and ultraviolet) [see George L. M., Biochemistry, 41, 7344-7349, (2002); Yigong Shi, Nature Rev. Mol. Cell. Bio., 5, 897-907, (2004)].
IAPs bind to and incapacitate caspases, a class of cysteine proteases involved in programmed cell death. Caspases bind to BIR (baculovirus IAP repeat) domain of IAPs, an approximately 70 amino acid zinc-binding motif. XIAP (human X chromosome encoded IAP), cIAP1 (cellular IAP1) and cIAP2 (cellular IAP2) each consists of three tandem adjoined BIR domains at the N-terminus, and other mammalian IAPs have one BIR domain. XIAP is the most effective caspase inhibitor among the IAPs class, which binds to both caspase-9 (the initiator caspase) and caspase 3/7 (the effector caspase), respectively. Even though the roles of cIAP1 and 2 in programmed cell death are still unknown, both bind to TNF-receptor 1 signaling complexes.
Smac/DIABLO (the second mitochondrial activator of caspase/direct IAP-binding protein with low pI), a polypeptide released from mitochondria during the apoptotic signal release, regulates the activities of IAPs by binding to the same sites to which IAPs bind. In addition, IAPs gene amplification and overexpression of IAPs have been found in many tumor cells.
For the above reasons, the resistance of tumor cells to apoptosis has been thought to be an important mechanism in tumor progression, and accordingly, there has been suggested that exploiting the difference between the mechanisms in tumor cells and those in normal cells may be as an effective anticancer therapeutic strategy. Further, such drugs must act selectively on cancer cells, exerting no adverse influence on normal cells.
Such drugs have been investigated by several international pharmaceutical manufacturers, as was disclosed in WO2008/073305A1, WO2008/073306A1, WO2008/016893A2, WO2006/107963A1, WO2006/113376A1, and WO2005/097791A1 by Novartis, WO2009/089502A1 and WO2008/079735A1 by Genetech, WO2007/131366A1 by Aegera, WO2008/014252A2 by TetraLogic, and others.
As to the methods for inhibiting IAPs, studies on Smac/DIABLO, a natural IAP inhibitory protein, structure mimetics are currently in progression. As a result, it has been found that the key sequence of alanine-valine-proline-isoleucine (Ala-Val-Pro-Ile, AVPI) is essential protein to bind with IAPs [see Yigong Shi, Nature structural biology, 8, 394-401, (2001)]. This key sequence (AVPI or AVPF) shows pharmacological activity of 120-500 nM in an in vitro assay, but failed to overcome its low cell permeability.
The present inventors have endeavored to search for compounds having AVPI properties of a natural IAP inhibitory sequence having good cell permeability, and to evaluate the activities of the compounds on cancer, inflammation, autoimmune diseases and neurodegenerative disorders. As a result, we have successfully identified a novel quinoline or quinazoline derivative having excellent, selective efficacies on IAPs.